It is in Silver-Gray, with black colorized Standard Buttons. This Theme replace the original blue Firefox 3 Layout. The theme developed specifically for guru of WEB, which don't like any colored features, and which want more worked space at browser.
This theme is just an updated version of RulerDark, with some extra new features the original version didn't have (like the much requested favicons in the bookmarks bar). Currently there's a version for Firefox 4 in the makings!